1. Field of the Invention
The present invention relates to an electrostatic actuator in which a movable member is driven by an electrostatic force, and a method of driving the electrostatic actuator, particularly, to an electrostatic actuator in which the movable member can be driven with a high accuracy, and a method of driving the electrostatic actuator.
2. Description of the Related Art
An electrostatic actuator in which the movable member is driven by an electrostatic force is disclosed in several publications, e.g., Japanese Patent Disclosure (Kokai) No. 8-140367, Japanese Patent No. 2928752, and “Electrostatic Linear Microactuator Mechanism” in “JOURNAL OF LIGHT WAVE TECHNOLOGY”, Vol. 17, No. 1, January 1999, IEEE”. In the electrostatic actuator disclosed in each of these publications, the electrodes are arranged as shown in, for example, FIG. 1, as disclosed in Japanese Patent No. 2928752 referred to above. In the electrostatic actuator shown in FIG. 1, a movable member 101 is arranged slidable between stationary members 102 and 103, which are arranged to face each other. While making the sliding movement between the stationary members 102 and 103, the movable member 101 is moved forward as denoted by an arrow 110 or backward in the direction opposite to the direction denoted by the arrow 110. Electrode sections 106 are formed in the movable member 101. On the other hand, two systems of stationary electrodes 102a and 102c, to which a voltage is applied at different timings, are alternately arranged in the stationary member 102. Likewise, two systems of stationary electrodes 103b and 103d, to which a voltage is applied at different timings, are alternately arranged in the other stationary member 103. The stationary electrodes 102a, 102c, 103b, 103d, which are formed in the stationary members 102 and 103, and the electrode sections 106 of the movable member 101 have substantially equal dimensions in the pitch and the electrode width. It should be noted that the stationary electrodes 102a and 102c formed in the stationary member 102 and the stationary electrodes 103b and 103d formed in the stationary member 103, the stationary electrodes 102a, 102c being positioned to face the stationary electrodes 103b, 103d, are arranged such that the phase of the arrangement is shifted from each other by ½.
If voltage is applied from a voltage source 104 to the stationary electrode 102a via a switching circuit 105 in the electrostatic actuator of the construction described above, an electrostatic force, i.e., the Coulomb force, is produced between the stationary electrode 102a and the movable electrode 106, with the result that the movable member 101 is attracted toward the stationary member 102 in a manner to permit the stationary electrode 102a and the movable electrode 106 to be overlapped with each other. Then, when the switching circuit 105 is switched from the stationary electrode 102a to the stationary electrode 103b so as to permit voltage to be applied to the electrode 103b, the movable member 101 is attracted toward the other stationary member 103 in a manner to permit the stationary electrode 103b and the movable electrode 106 to be overlapped with each other. Further, when the switching circuit 105 is switched from the stationary electrode 103b to the stationary electrode 102c so as to permit voltage to be applied to the stationary electrode 102c, the movable member 101 is attracted again toward the stationary member 102 in a manner to permit the stationary electrode 102c and the movable electrode 106 to be overlapped with each other. Still further, when the switching circuit 105 is switched from the stationary electrode 102c to the stationary electrode 103d so as to permit voltage to be applied to the stationary electrode 103d, the movable member 101 is attracted again toward the stationary member 103 in a manner to permit the stationary electrode 103d and the movable electrode 106 to be overlapped with other. It follows that, if voltage is successively applied to the stationary electrodes 102a, 103b, 102c and 103d by switching the switching circuit 105, the movable member 101 is macroscopically moved forward in the direction denoted by the arrow 110 while being microscopically vibrated between the stationary members 102 and 103. On the other hand, if voltage is applied successively to the stationary electrodes 103d, 102c, 103b and 102a in the order mentioned, the movable member 101 is moved backward macroscopically in the direction opposite to the direction denoted by the arrow 110.
In the electrostatic actuator of the construction described above, it is necessary to align the paired stationary members 102 and 103 with a high accuracy. It is also necessary to form equidistantly the electrodes of the same width in the stationary members 102 and 103 with a high accuracy. Such being the situation, a sufficient time and a sufficient labor are required for manufacturing the parts of the electrostatic actuator and for assembling the manufactured parts with a high accuracy. It follows that the manufacturing cost of the electrostatic actuator is increased, which generates a problem that must be solved for achieving mass production of the electrostatic actuator.
As described above, in the conventional electrostatic actuator, it is necessary to position accurately the two stationary members 102 and 103 and to set the phase of the alignment between the two with a high accuracy. It is also necessary to form accurately the electrodes on the two opposite surfaces of the movable member 101, with the result that a sufficient time and a sufficient labor are required for assembling the actuator mechanism. It follows that the manufacturing cost of the electrostatic actuator is increased so as to generate a problem that must be solved for achieving the mass production of the actuator mechanism.